A PMC Sig conversation: "Complex project or just poorly scoped?"

Are "complex projects" real or are they simply a result of poorly defined scope. How can one distinguish between a genuinely complex project and one that has not had its scope and context sufficiently developed?

Complex projects seem to be the 'new thing' and recently the PMC SIG joined the London branch at an event held at Atos with several speakers with an interest and expertise in these areas who gave a short presentation for and against and then opened the debate with a few 'scientifically valid' votes thrown in.